@Handy Plough
Are you sure? I think you're mistaken. FYI, gmail is not on the top of the ALL search results when looking for "mail" keyword:
As you can see only the German result puts gmail at the top. In the .com and .ru option, you get yahoo and mail.ru,resp., above gmail. So this might indicate that Google do not really put their own products above their competitors, relevance could be their main priority. Interesting, that bing does a similar thing there.
This happens when gmail is the most popular mail service on the planet. So are saying that Google should intentionally underrate their products below their own products promoting their competitors'?